Warming a stone tiled floor

Hi I am rebuilding an old stone house in Cote D Azur and installing air-to- air reversible heating/AC in ceiling. But I would like to be able to have a slight heat under the stone tiles during winter. The electrician says its very expensicve to run, and difficult to control the heat. The room is approx 50 sq. mars.(540 sq. feet). Any experiences/advice?

underfloor heating, romans used hot air (difficult to find servants nowadays to do the fires and fan the air around, we used a hot water system in Scotland, worked well, but needs a heatsource like oil, wood burner,
in a bathroom we used an electric heat mat to just warm the floor (main heat came from a radiator/towelrail) . These mats are very thin, can be laid under tiles (in the screed) and use very little electricity. Suggest you try sourcing from the UK as they are not common in France.
something alike

You might want to edit your last post and remove phone number.

We have air to water underfloor heating and it works a treat. A nice gentle source of heat and efficient. No idea whether air to air is similar.

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Ha ha, thanks

The trouble is that edits remain visible, I’ve arranged that the version with your phone number is hidden from view.

It depends where you’re at in the process and what source of heating you have.

Water fed systems work very well - but they need connecting to a boiler or something. They make the air pumps much more effective. It’s not a 5 minute job

Electric is fine for small spaces but expensive for larger spaces (it’s 100W a sq metre for the basic kits …that’s a lot multiplied by 50). It works well in taking the chill off and it works well in small spaces. My tiny

Thanks, will start from scratch, new concrete base. Checked a danish brand Heat Map, ranging from 68-200 watt pr square metre.

Insulation under the slab? Or above?

If one wants ‘instant on’ then it will be difficult to control. Heating timescale is likely to be hours depending on the power of the heaters and the mass of material the heat has to warm. It’s likely to be ideal as a background heat that can be boosted with additional heating if needed in the context of a home.

Dutch friends put “underfloor” in their kitchen/livingroom and, as you say, it just gives some gentle warmth underfoot…

As the kitchen door is the one entrance/exit to the house, it’s open/closed quite often and the cold air swoops in. Underfloor could not keep up with this, let alone make the room warm enough to sit in…
they now have a glorious logburner which heats the kitchen/living room and wafts up to the bedrooms as well.
but the underfloor is still lovely, first thing in the morning when one potters downstairs in barefeet… :+1:

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Over the slab

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is it a bit like an electric blanket… ie an electric carpet ???

yes, its 3 mm thick only

and do you then put a carpet over the top??? I’m trying to imagine it… and thinking I’d need a large sign “remove your shoes, please” :wink: … especially high-heels :wink: :wink:

I love the idea of snuggling my toes into a warm, tufty carpet…

That will definitely help with electric matts as they are not as warming as a wet system that warms the slab in most cases. Be interested to hear how it works out. One job I was on had according the the sales particulars, underfloor heating to the kitchen. With my thermal imaging camera we could just make out where the mats were placed but the builder had been very economic shall we say. Increase in temperature over ambient was about 2c because they either only put down 2 matts or didnt connect the others :joy:

In 2000 we did a major renovation on our family home in Dublin, a knock and rebuild really, doubling its size. I put in underfloor heating downstairs but traditional rads upstairs, all run by an efficient (in the day) gas boiler. I also insulated the house very well by 2000 standards.

After the renovation and when we had been living with U/F heating for a while I remembered, too late, a comment an architect uncle had made during a conversation when he was dropping me off to school years earlier. I don’t remember the context (we had great conversations :slightly_smiling_face:) but it was to the effect that storage heaters, for that is what U/F heating is, gives the heat today that you needed yesterday. In other words, if yesterday was sunny and warm the system would have allowed the slab to cool and if there was a cold snap today the slab would take too long to warm up and cope, and vice versa. So I’m firmly of the opinion that U/F is a very good idea in a climate (or microclimate) where the weather is consistent, which is certainly not the case in Dublin. (Unless miserable is the description :face_with_hand_over_mouth:).

So our U/F was very inefficient, despite having six or seven separately controlled zones we could “fine tune” via the stats or alter the flow from the manifold. I had to drive it hard so that we weren’t chilly during cold snaps and thus it was very expensive to run, eye-wateringly expensive. It was cosy though, and that was nice for our little family :slightly_smiling_face: which at the end of the day was all that mattered.

Now, even had we known that, we probably would have gone ahead for aesthetic reasons, we had large areas and lots of very well insulated glass and rads downstairs would have ruined it. But when I was living here and only my student daughter was rattling around the family home massive bills were thumping onto the doormat to just keep one person toasty. That ended when she graduated, did her intern year and went off to Oz in 2019 and I flogged the house and downsized. I often wonder, given energy prices now, what the bills for our old house are like.

When I renovated this house in France in 2004 I put in air to air reversible clim in each room with electric U/F in the salon and bathrooms. The bathrooms are brilliant in winter but we don’t use the U/F in the salon for the same variability reason, chilly one day, doors and windows, open the next.

BTW, I know there are now systems that look at the weather forecast and try and predict how warm the slab should be for those conditions, but I’d wonder at its responsiveness and I’d like to see it in action before committing to U/F again.


Great feedback and yes same issues as storage heaters so best during the long cold periods. Interesting that you insulated very well as that should by todays standards provide a far mor stable environment which would require far less heating so a low background heat could work. Even new gas boilers have external temperature sensors so they can modulate the boiler’s performance. Cant believe it took that long to sort that out,


Ah… it has to be embedded in a screed… 'nuff said… won’t do in my kitchen then…

I’ll invest in snug slippers for winter… :wink: